Blasting explosive containing a water-soluble polysaccharide ether



Patented June 1, 1954 BLASTING EXPLOSIVE CONTAINING A WATER SOLUBLE ETHER POLYSACCHARIDE Samuel Henry Davidson, Largs, Scotland, as-

signor to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application August 13, 1951, Serial No. 241,687

Claims priority application Great Britain August 31, 1950 7 Claims.

occasioned by the extreme water solubility and L hygroscopicity of ammonium nitrate, including the. rapid deterioration of cartridges containing ammonium nitrate powder and semi-gelatine explosives when the shots are laid in wet situations, are minimised by the inclusion in the composition of the explosive of a water-swellable and watersoluble ether of a macro-molecular polysaccharide, for instance a water-swellable and water-soluble ether of cellulose or of starch, a proportion of the said ether rangin from /2 to 5% of the weight of the explosive composition being conveniently included. It is also stated that when the explosive cartridge is submerged under water it would appear that the water-swellable and water-soluble macro-molecular polysaccharide ether swells up when it comes into contact with the water and forms a surface protection for the interior of the mass of the explosive in'the cartridge because of the low mobility of the swollen mass and the slow rate at which it in terdiffuses with the surrounding water... In said.

tion of a flame quenching and cooling ingredient,v

and one of the most. efiective. of these came quenching and cooling ingredients is sodium chloride. 4

There are however advantages to be gainedin safety and other characteristics in safety blasting explosivesof the aforesaid kind by the replacement of the ammonium nitrate by equivalent amounts of sodium nitrate and ammonium chloride, with a corresponding partial or complete elimination of added sodium chloride. The resulting explosive compositions however are still hygroscopic and quickly deteriorate in sensitiveness when used in wet situations. a

We have now found that safety explosive compositions free from added ammonium nitrate but including sodium nitrate and ammonium chloride in association with explosive sensitising ingreclients and optional additional constituents, whether of powder or semi-gelatine or even gelatine consistency, are rendered suitable for use in wet situations by the inclusion in the composition of a water-swellable and water-soluble macromolecular polysaccharide ether, for instance a water-swellable and water-soluble ether of cellulose or of starch.

According to the present invention safety blasting explosive compositions are free from ammonium nitrate and comprise sodium nitrate, ammonium chloride, at least one explosive sensitising agent, and a water-swellable and watersoluble macro-molecular polysaccharide ether.

The water-swellable and water-soluble macromolecular polysaccharide may be for instancea water-soluble methyl cellulose, a water-soluble methyl ethyl cellulose, a water-soluble hydroxy ethyl cellulose or a water-soluble sodium salt of a carboxymethyl cellulose. As an example ofv a suitable water-swellable and water-soluble starch other a water-soluble sodium salt of carboxymethyl starch may be used.

The quantity .of theaforesaid water-swellable and water-soluble macro-molecular polysacchar ides may conveniently be from /2 to 5% of the weight of the explosive composition.

It is preferred to mix the above water-swellable and water-soluble macro-molecular polysaccharide ethers with the inorganic salts or with the other combustibles before incorporating these with the other ingredients of the explosive, although it is also possible to incorporate the water-swellable and water-soluble ethers into the,

finished explosive with equally efficacious results.

Preferably according to the present invention the composition also contains a small proportion of a calcium salt of a high molecular weight fatty acid, for example calcium stearate. This confers on the composition a certain water repellentef feet which is useful in delaying the wetting of even the surface of the explosive cartridge, especially when the situation in which it is used is only slightly wet, andit does not. interfere with the eiiicacy of the ether of the macro-molecular polysaccharide in swellin up and protectingthe interior of the explosive cartridgeif and when the Water overcomes the effect of the calcium 3 stearate and succeeds in wetting the surface. A proportion ranging from A1 to of the weight of the explosive composition may advantageously be included.

ing a 80:20 mixture of glycerine and ethylene glycol, are run on to the nitrocellulose and the woodmeal which is then hand stirred and when the mixture has become at least partly gelatinised The invention is especially applicable to ex- 5 it is transferred to an Atlas (registered tradeplosive compositions of powder and semi-gelatine mark) mixer in which the sodium nitrate, the consistency, since these normally deteriorate ammonium chloride, and the calcium stearate more rapidly than explosives of gelatine conand the sodium salt of the carboxymethyl cellusistency when they are used in wet boreholes lose and the china clay have already been inunder such conditions that the water has access troduced and mixed together. During the action to the composition. of the machine thereafter the wheatfiour is The following table illustrates how the replaceworked in. The action of the machine is conment of 1.5% of woodmeal in the composition tinued until the ingredients are well incorporated of MH 36 by 1.0% disintegrated water-soluble together. The resulting semi-gelatine explosive sodium carboxymethyl cellulose and 0.5% calcomposition is cartridged and provided with cium stearate to give the composition MI-I 3'7 waxed paper wrappers. Detonation of the carimproves the waterproofness 32 to 60 times and tridges of the explosive can still be satisfactorily how the replacement of 1.5% of woodmeal in initiated by means of a No. 6 commercial detothe composition of MH 38 by 1.0% disintegrated nator after storage under 6 inches of water for water-soluble sodium carboxymethyl cellulose more than 48 hours, even though the cartridge and 0.5% calcium stearate to give the composiwrapper has been artificially perforated at severtion MI-I 39 improves the waterproofness about a1 points. These cartridges are suitable for 12 times; and how by increasing the percentage blasting coal in fiery or dusty mines. of disintegrated water-soluble sodium carboxy- The water-soluble sodium salt of carboxymet yl cellulose by 2.5% in MH '7 to give the methyl cellulose in the above example contains composition ME 58 the waterproofness is in- 0.75 sodium carboxymethyl groups per anhydro creased about 3.5 times, and by increasing the glucose unit of cellulose. percentage of disintegrated water-soluble sodi- Similarly perforated cartridges containing a um carboxymethyl cellulose in Nil-I59 by 2.5% composition similar to the above except that the and leaving out the 1% wheatfiour the waterwater-soluble sodium salt of carboxymethyl celproofness is increased about 2.5 times. The table lulose is replaced by 1% woodmeal or other inalso shows that the replacement of 1.5% Woodsoluble cellulosic material and thus not in acmeal in the composition of ME 36 by 1.5% discordance with the invention, cannot be caused integrated water-soluble sodium oarboxym t y to detonate by means of a similar detonator after cellulose to give the composition ME 57 improves standing under 6 in h of 1d at for 15 the waterproofness 32 to 60 times and how the mi t replacement of 1.5% woodmeal in the composi- What I l im 1 tion MH 38 by 1.5% disintegrated Water-soluble 1. Safety blasting explosive compositions comsodium cerbo y y cellulose to give the prising sodium nitrate, ammonium chloride, at 11051111011 ME 59 improves the W D eS 5 40 least one explosive sensitising agent, and a waterto 6 times. swellable and Water-soluble macro-molecular MH36 M1337 MH57 M1158 M1138 M1139 M1159 M1160 sire-555a; i: ii 6:2 5:5 -339- Nitrocellulose. 0.25 0.25 0.25 0.25 0.5 0.5 0.5 0.5 Wooomooi 3.85 2.35 2.35 1 75 3.5 2.0 2.0 2.0 Wheatflour .0 -0 .0 Ammonium chlor 32.4 32.4 32.4 51 9 28.5 28.5 28.5 28.0 Sodium nitrate. 51.4 51.4 51.4 50.0 45.5 45.5 45.5 44.5 China clay 4- 0 4. 0 4. 0 4. 0 Disintegrated water-soluble s0- 1.0 1.5 4.0 1.0 1.5 4.0 Calcium stem-ate 0. 5 0- 5 Waterproofing test hIS 54 8-15 8-15 32-48 4-5 48-72 24-32 55-72 The invention is further illustrated by the folpolysaccharide ether selected from the group lowing example in which the percentages are by consisting of a polysaccharide ether of starch Weight and a polysaccharide ether of cellulose, said ether Example being homogeneously distributed throughout the Percent 0 blasting composition. A mixture of nitroglycerine and ethylene 2. Safety blasting explosive compositions as glycol dinitrate in the ratio 80:20 17.0 claimed in claim 1 wherein the proportion of Nitrocellulose 0- aid water-swellable and Water-soluble macrosodium nitrate lecular polysaccharid ether ranges from 1A2 Ammonium chloride 23-5 t0 5% 0f the weight of the explosive. Woodmeal 2. 3. Safety blasting explosive compositions as Wheatfiour l im d in Claim 1 wherein the said waterchma c1ay wellable and water-soluble macro-molecular Water-soluble sodium salt of carboxymethyl polysaccharide ether is a water-swellable and cellulose whereof a 1% solution has a pH soluble ether of cellulose.

of 6 to 9 and a viscosity of 30 to 70 cps.

at 20 C. Calcium stearate 0.5

is prepared in the following manner. The mixed liquid nitric esters, which are prepared by nitrat- 4. Safety blasting explosive compositions as claimed in claim 1 wherein the said water-swellable and water-soluble macro-molecular polysaccharide other is a water-swellable and soluble ether of starch.

5. Safety blasting explosive compositions as claimed in claim 1 wherein the composition includes a proportion of a calcium salt of a high molecular weight fatty acid.

6. Safety blasting explosive compositions as claimed in claim 5 wherein the calcium salt of a high molecular weight fatty acid is calcium stearate.

7. A blasting cartridge containing a safety blasting explosive composition comprising sodium nitrate, ammonium chloride, at least one explosive sensitizing agent, and a water-swellable and Water-soluble macro-molecular polysaccharide ether selected from the group consisting of a polysaccharide ether of starch and a polysaccharide ether of cellulose, said ether being homogeneously distributed throughout the blasting composition.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,550,064 Ehrlich Aug. 18, 1925 2,154,416 Tyre Apr. 11, 1939 2,231,044 Winning Feb. 11, 1941 2,570,827 Madison et a1. Oct. 9, 1951 FOREIGN PATENTS Number Country Date 359,163 Great Britain Oct. 22, 1931 645,039 Great Britain Oct. 27, 1950 984,674 France July 9, 1951 OTHER REFERENCES Hollabaugh et al., Ind. and Eng. Chem., vol. 37 (1945) pp. 943-947. 

1. SAFETY BLASTING EXPLOSIVE COMPOSITIONS COMPRISING SODIUM NITRATE, AMMONIUM CHLORIDE, AT LEAST ONE EXPLOSIVE SENSITISING AGENT, AND A WATERSWELLABLE AND WATER-SOLUBLE MACRO-MOLECULAR POLYSACCHARIDE ETHER SELECTED FROM THE GROUP CONSISTING OF A POLYSACCHARIDE ETHER OF STARCH AND A POLYSACCHARIDE ETHER OF CELLULOSE, SAID ETHER BEING HOMOGENEOUSLY DISTRIBUTED THROUGHOUT THE BLASTING COMPOSITION. 